The Classic prosthesis for the amputee of a hand or forearm is the "hook", archaic in a sense and in no way comparable to the anatomy of the natural hand; mechanically or cosmetically. It is the prehensile grip and natural appearance that has been lacking in the prior art, and though mechanical arms and hands have been devised, they have been overly complex, excessive in weight and unnatural in both function and appearance. Accordingly, it is a general object of this invention to provide a prosthesis which involves the hand and forearm and provides the natural prehensil function and natural cosmetic value as well.
The human body involves a skeletal frame that supports the flesh, the composite of which involves bone, muscle, fat, and a covering of skin, and the total of which has a certain mass and firmness associated with rigidity. In other words, the parts and limbs of the human body have certain expected physical qualities as well as mechanical functions which enable man to perform. In this case under consideration it is dexterity which is to be reestablished with the amputee, enabling him to perform substantially as before, it being an object herein to provide a prosthesis that operates in a releasible prehensile mode to grip objects the same as a natural hand. With the present invention, all mechanical, there is a thumb that moves in opposition to the index and/or middle finger, to establish a prehensile grip therebetween. Note that there are two or three gripping members. It is also an object of this invention to provide such a prosthesis wherein the mass and firmness is natural, from both the standpoint of feeling and appearance.
The anatomy and movement of body members involves motor means and coupling means to the members to be moved. It is the hand and its moveable finger members with which this invention is primarily concerned, it being an object herein to replace the muscles and tendons that formerly motivated the fingers of the amputee. Accordingly the hand is replaced mechanically as well as cosmetically, and the muscle and tendon complex is replaced by motor means and coupling means operating the mechanical hand in a natural way. In practice, it is the remaining body motions and functions that are employed as the motivating power, under mental control to be governed by the intelligence of the amputee. As will be described, it is assumed that the upper arm and a portion of the lower arm remain intact, in which case it is the relative angular displacement between the humerus and what remains of the radius and ulna that is employed to operate the prehensil movement of the three aforementioned mechanical fingers; the thumb as it is opposed to the index and middle finger.
The prosthesis as it is disclosed herein resembles a forearm and natural hand in every respect, having an extension of the radius and ulna, having carpal and meta-carpal sections, and having each of the proximal, middle and terminal phalanges of the fingers. It is an object of this invention to articulate these mechanical phalanges in a natural manner, so that they are free to move together and so that the thumb is prehensile with respect to the index and middle finger. Principally, it is the proximal phalanges or long bone of the finger that is to be moved as a lever, and with the middle and terminal phalanges carried thereby to be moved therewith. However, a natural feature of this invention is the articulation of one or more phalanges as may be desired; in each case the phalanges having restricted inward and outward movement with respect to the metacarpal section carrying the same. In practice and as shown herein, the middle finger has a spring biased (to close) proximal (middle and terminal) section that straightens when opposed by an object pressured by the thumb. It is to be understood that any one and/or all of the finger joints can be simulated as described herein.
The motor means and coupling means to the mechanical fingers provided as herein above referred to is unique with the present invention, simulating the tendon system of the natural arm and hand. However, the motor and coupling system herein disclosed is simplified and practical, as it employs flexible members anchored to the amputee's upper arm above the capitulum of the humerus and extended to the proximal phalanges to be moved. A feature is the coordinated movement of both the thumb and the opposing index and/or middle finger, whereby the opened prosthesis can be closed upon an object in a natural prehensile manner. Another feature is the positive action of a pull cord system which also includes buffer means that permits over travel of the arm extension of the amputee while increasingly applying prehensile gripping force. Accordingly, the amputee can intelligently apply increased grasping pressures as circumstances require.
It is to be understood that the anatomy to be replaced varies widely according to deformation and injury to a person's body, so that it may be the thumb or any one or more of the fingers that must be replaced, it being an object herein to replace any one of the fingers as herein disclosed. Fundamentally, it is the skeletal frame that is reestablished and all of which is covered by an envelope or glove of plastic material of thickness, softness and suppleness to simulate the skin and finger pads of a real hand. Color, surface texture and imperfections (wrinkles etc.) are included along with fingernails of horn-like plastic; and manicured to match the real hand. Accordingly, realism is achieved with the present invention, for practical as well as for psychological purposes.
A characteristic feature of the human arm and hand appended thereto is the natural ability to revolve the same through approximately 270.degree.. This ability is due to the interaction of the radius and ulna, a function which is effectively destroyed when these two bones are severed. It is an object herein to substitute this rotatability by providing rotation of the prosthesis at the wrist portion between the hand and socket which carries the same. Further, it is an object to avoid unnatural rigid connections of the arm and hand, and with present invention there is flexibility therebetween without adverse effect upon the aforementioned prehensile grip which is so necessary.
The foregoing and other various objects and features of this invention will be apparent and fully understood from the following detailed description of typical preferred form and application thereof, throughout which description reference is made to the accompanying drawings.